Immune cells play a key role in cancer development, maintenance, invasion and metastases. However, while some specific cellular interactions and functions are relatively well understood, other aspects of immune responses in cancer remain entirely unknown. Several outstanding questions include: a) how do interactions occur in real-time in vivo across different cancers? b) how do cytotoxic and other anti-cancer drugs affect the complex immune network in tumors? and c) can drugs that harness immune function be used in a synergistic fashion to enhance anti-cancer efficacy? Until recently it has been difficult to answer such questions since it has not been possible to visualize immune cells within their natural microenvironment. In this project, we will systematically image key immune cells using real-time imaging technologies, and investigate how different anticancer therapies affect their behavior. We hypothesize that commonly used drugs do indeed affect immune cell behavior, and that they can be chosen and/or combined so as to offer additive synergistic anti-tumor effects. Our specific aims are as follows: 1) To determine the composition and function of tumor-infiltrated immune cell networks in a mouse model of colon adenocarcinoma. We achieve this by first establishing all the necessary tools for intravital imaging. 2) To determine how anti-cancer drugs modulate immune networks in the mouse model of colon adenocarcinoma. To achieve this, we will investigate commonly used cytotoxic drugs, new and promising molecularly targeted agents, as well as NCI top-listed immune agents. Individual drug effects will be studied first, before subsequently investigating the effects of rationally selected drug combinations. 3) To extend our most promising treatment regimen to orthotopic and transgenic mouse cancer models, which better replicate human disease. Clinical translation will be further facilitated by measuring treatment responses using clinically relevant readouts. Ultimately, our goal is to revise current therapeutic options for cancer. To this end, because the proposed work is focused on evaluating clinically approved agents, our findings will not only have high clinical significance but will also be rapidly translatable. This project will employ innovative approaches to study immune interactions and function in real-time. The combined use of genetically engineered mouse models of human disease together with state-of-the-art microscopic imaging approaches will be facilitated through productive collaborations.